Many control systems include multiple sensors to monitor various system parameters and thereafter communicate this system information back to the controller. Each sensor generates an output signal, which is read by the controller, in preparation for subsequent system control. However, it is often difficult to discern the true signal from the noise if the noise includes a similar frequency as compared to the true signal. One known solution includes utilizing a band pass filter to filter noise at a first frequency and thereafter allowing the true signal frequency, which is at a second differing frequency, to pass through the filter.
Known filtering techniques include utilizing a band pass filter to filter out noise which may be characterized within a first frequency band and to allow the true signal, which may be characterized within a second and different frequency band, to pass through the filter. However, band pass filters are often not acceptable since the frequency of noise may be similar to the frequency of the true signal when the signal is prone to fluctuation. Moreover, since the band pass filter is a passive element its effectiveness in providing a quality signal is significantly dependent on the range of signals being filtered.
For example, U.S. Patent Application Publication No. US 2001/0020789, dated Sep. 13, 2001 to Nakashima, discloses utilizing look-up tables or maps identifiably based on desired motor/generator torque to provide the appropriate level of signal filtration. The signal from the torque sensor is input into a response characteristic compensation section of the motor/generator controller, such as a first order low pass filter that transmits or passes signals at a frequency below a given cutoff frequency, and attenuates signals with a frequency above the given cutoff frequency. Unfortunately, if the torque output signal is similar in frequency to that of the system noise, then the filter is likely to become less effective.
Furthermore, many output signal types for use on high performing systems, such as torque control of an electric motor, for example, require the ability to aggressively control the motor to obtain certain performance mandates. In response to the need to provide aggressive response to the speed/torque signal of an electric motor, the electric motor tends to experience high frequency torque oscillations, which can result in instability and/or surging of the motor. Moreover, high frequency oscillations may cause undesirable operational noise, reducing the useful life of the motor, and/or adversely effecting operator comfort in instances where the electric motor is utilized to animate a work machine, for example.
The present invention addresses one or more of the aforementioned problems.